"I saw him as a normal guy, an every day guy, doing every day things,” said Mai's 16-year-old son, Anthony.

San Diego police arrived Friday morning at a Rancho Peñasquitos neighborhood after the alleged shooter's mother called at around 6 a.m., officials said

"We're only here to preserve peace, not to conduct an investigation," Lt. Andra Brown said. "Other agencies are here to investigate."

Arlene Holmes has identified herself to reporters as the mother of the suspected shooter. Her son went to high school in San Diego and then attended college in Colorado, Brown said. Authorities described him as a loner.

Poway Unified School District in San Diego confirmed that Holmes was a 2006 graduate of Westview High School.

Holmes, 24, was taken into custody early Friday in the parking lot outside the Century 16 movie theater after the post-midnight attack in Aurora, Colo. He allegedly entered the theater through an exit door about half an hour into the local premiere of the Batman movie "The Dark Knight Rises." At least 12 people were killed in the attack.

Witnesses described a chaotic scene, telling television reporters that they were overcome by noxious gas unleashed by the suspect just before he started shooting, and that they had to decide between staying on the ground, helping wounded victims or running away before the gunman was able to reload his weapon. Survivors said they were forced to run past bodies in the aisles.

The attack was smoky and surreal, witnesses reported, as moviegoers, some wearing their own costumes, slowly realized that bullets were flying from the weapon of the man in body armor whose face was hidden by a gas mask.

"There were bullet [casings] just falling on my head. They were burning my forehead,” Jennifer Seeger told reporters afterward. “Every few seconds it was just: Boom, boom, boom," she said. "He would reload and shoot and anyone who would try to leave would just get killed."

The shooter was armed with a rifle, a shotgun and two handguns, police said. Cellphone videos from the scene show panicked moviegoers running -- some screaming -- and others with blood visible.

One theory of the attack is that Holmes may be a disgruntled employee of the movie theater, based on the fact that he allegedly was able to enter through an exit, sources said.

More than 20 SWAT team members were gingerly searching Holmes' apartment on Paris Street, a process that could take hours or even days because the apartment appeared to be booby-trapped with explosives, Aurora Police Chief Dan Oates told reporters.

The area around the apartment, on the third floor of a housing complex, has been evacuated.